1. Field
The present disclosure generally relates to multi-chip modules (MCMs). More specifically, the present disclosure relates to an MCM that includes substrates that are mechanically coupled using magnetic components.
2. Related Art
As integrated-circuit (IC) technology continues to scale to smaller critical dimensions, it is increasingly difficult for existing inter-chip connections to provide suitable communication characteristics, such as: high bandwidth, low power, reliability and low cost. A variety of interconnect technologies have been proposed to address this problem, including proximity communication or PxC (for example, using capacitive inter-chip contacts).
PxC based on capacitive inter-chip contacts provides dense inter-chip connections, with a pitch between neighboring pads on the order of 10-100 μm. However, PxC introduces additional packaging challenges. In particular, in order to achieve high-bandwidth/high-data-rate inter-chip communication, PxC typically requires mechanical alignment between facing chips on the same order as the pitch between neighboring pads. In addition, in order to allow chips in multi-chip modules (MCMs) that use PxC to be replaced (as needed), a remateable assembly technique is desirable.
One purely mechanical assembly technique that provides highly accurate and remateable mechanical coupling of chips in an MCM includes balls and pits. In this assembly technique, adjacent chips in the MCM are aligned by placing the balls into collocated pits on surfaces of the chips.
An existing MCM that includes balls and pits is shown in FIG. 1. In this MCM, island chips (such as processors) are placed face-down, and a bridge chip is placed face-up. Note that the chips receive signals, power and ground from the package substrate through C4 solder and/or copper pillars as level-one interconnects, and that the bridge chip communicates with the chips using PxC.
Typically, there are mechanical clearances, h1, h2 and h3, between the components in this existing MCM. However, given these mechanical clearances, it is difficult to remateably support the bridge chip in FIG. 1 while maintaining the alignment of the balls and pits. For example, because of mechanical clearance h3, if the balls are merely placed into the pits (which provides remateable mechanical coupling) there is no normal or restoring force to oppose the force of gravity on the bridge chip. Consequently, the bridge chip will fall away from the island chips, which results in misalignment and poorer PxC.
Hence, what is needed is an MCM without the above-described problems.